Contact lenses have been used commercially to improve vision since at least the 1950s. The first contact lenses were made of hard materials and as such were somewhat uncomfortable to users. Modern soft contact lenses are made of softer materials, typically hydrogels. Many wearers still wear soft contact lenses formed from hydrogels.
Recently soft contact lenses made from silicone hydrogels have been introduced. Silicone hydrogel are water-swollen polymer networks that have improved oxygen permeability. These lenses provide a good level of comfort to many lens wearers, but there are some users who experience discomfort and excessive ocular deposits leading to reduced visual acuity when using these lenses. This discomfort and deposits has been attributed to the hydrophobic character of the surfaces of lenses and the interaction of those surfaces with the protein, lipids and mucin and the hydrophilic surface of the eye.
Others have tried to improve comfort and reduce deposits on contact lenses by incorporating at least one polymeric wetting agent into either or both of the contact lens matrix or packaging solution.
Cyclic polyamides, such as polyvinylpyrollidone and acyclic polyamides, have been incorporated into both conventional and silicone containing hydrogel formulations and contact lenses. Poly(meth)acrylamide and N-substituted poly(meth)acrylamides have been disclosed to be hydrophilic IPN agents which may be incorporated into conventional (non-silicone containing) hydrogels.
Modifying the surface of a polymeric article by adding polymerizable surfactants to a monomer mix used to form the article has also been disclosed. However, lasting in vivo improvements in wettability and reductions in surface deposits are not likely.
Polyvinylpyrrolidone (PVP) have been added to hydrogel forming compositions to form a semi-interpenetrating network which shows a low degree of surface friction, a low dehydration rate and a high degree of biodeposit resistance. High molecular weight hydrophilic polymers, such as PVP have been added as internal wetting agents into silicone hydrogel lenses, however such polymers can be difficult to solubilize in reaction mixtures which contain silicones.
Block copolymers having hydrophobic blocks and hydrophilic block have also been disclosed as suitable for incorporating into or onto hydrophobic substrates, including silicone hydrogel contact lenses. However, the hydrophobic blocks require special polymerization steps and can decrease the hydrophilicity of the hydrophilic polymer.
Therefore it would be advantageous to find additional high molecular weight hydrophilic polymers which may be incorporated into a lens formulation to improve wettability of the lens without a surface treatment.